CA2196758C - Temperature control of near-infrared analyzer - Google Patents
Temperature control of near-infrared analyzer Download PDFInfo
- Publication number
- CA2196758C CA2196758C CA002196758A CA2196758A CA2196758C CA 2196758 C CA2196758 C CA 2196758C CA 002196758 A CA002196758 A CA 002196758A CA 2196758 A CA2196758 A CA 2196758A CA 2196758 C CA2196758 C CA 2196758C
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- Prior art keywords
- temperature
- cabinet
- heat exchanger
- heat
- internal
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- Expired - Fee Related
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- Investigating Or Analysing Materials By Optical Means (AREA)
- Control Of Temperature (AREA)
Abstract
A preferred temperature control strategy was devised to remove heat from the analyzer and control the optical bench temperature continuously at aim. A foil-type RTD temperature detector is fastened to the optical bench to serve as a measurement input device for a PID control strategy, which is truly aim-seeking. The control strategy employs a heat pipe technology to remove heat from the analyzer enclosure. A heat pipe utilizes a fluid (such as an alcohol) to remove heat by evaporation of the fluid at an internal air circulation heat exchanger and then recondensing the fluid at an external air circulation heat exchanger. The PID temperature controller achieves the desired temperature setpoint by manipulation of heat exchanger fan speeds. The heat removal rate can be very precisely controlled. In practice, both heat exchanger fans could be controlled together, however, to achieve optimal internal temperature uniformity, the internal heat exchanger fan is maintained at full speed and just the external fan is controlled to adjust heat removal rate. Optical bench temperature control is maintained to plus or minus 0.1 degree C
vs. a typical temperature control band of plus or minus 2 degrees C.
vs. a typical temperature control band of plus or minus 2 degrees C.
Description
HT-340D 2 i 96758 ''ro.~-°s96 Temperature Control of Near-Infrared Analyzer -.S ~ $dCkgT'O and O 11e T V T~ ~ OI1 ._ The invention relates to thermal management in ir_strumentation and more particuharly it relates to temperature control of a-near-infrared analyzer.
Thermal management-in instrument packaging has always been an impcrtant design consideration. Internal temperature control or near-infrared (NIR? analyzers is-essential for measurement precision. More particularly, NIR spectrophotometers- can be affected by temperature variations as little as 2.to 4degrees C, which cause shifting of optimal wavelengths, and the addition of error -in the measurement.
The typical process spectrophotometer is controlled within.a band cf temperature by utilization of an on-off type control strategy. In the "on" state, a condenser or .__. -other device is turned on to remove heat build-up from within the spectrophotometer enclosure as is described in U.S. Pater_t No. 4,328,676. The condenser or other device remains "on" until a low temperature limit is reached anal then the condenser is turned "off." The-temperature in -the spectrophotometer enclosure rises from the heat generated by the electronics and/or tile external environment until a second temperature limit is reached, which causes the condenser or other device to be turned -"on" again. This on/off temperature control approach commonly al7.ows the internal temperature to cycle 2-~ C
degrees..
SLT~!aZ'V of th Tnvon t i nn A preferred temperature control strategy was devised to remove heat from the analyzer and control the optical bench temperature continuously at aim. A temperature sensor is fastened to the optical bench in an analyzer to serve as a measurement input device for a control strategy which is truly aim-seeking.- The control strategy employs w heat pipe heat exchanger to remove heat from the F~Ai~~,7~~ ~H~Gi WO 96105545 , 219 6 7 5 8 PGTIUS95I08968 analyzer enclosure. A heat pipe utilizes a fluid (such as an alcohol) to remove heat by evaporation of the fluid at an internal air circulation heat exchanger and then recondensing the fluid at an external air circulation heat exchanger. Heat pipes are particularly useful in that internal cabinet air, not outside air, is circulated through the critical optical components, thereby , eliminating the need for additionalfiltering of the cooling air.
A PID temperature controller achieves the desired temperature setpoint by manipulation of heat exchanger fan speeds. The heat removal rate can be very precisely controlled..,T~ practice, both heat exchanger fans could be controlled._together; however, to,achieve optimal internal temperature uniformity, the internal heat exchanger fan-is maintained at full speed and just the external fan is controlled to adjust heat removal rate.
Optical-bench temperature control is maintained to plus or minus 0.1 degree C vs. a typical temperature control range of plus or minus 2 degrees C.
More particularly, the invention includes an apparatus and-a process for controlling the temperature of an analyzer cabinet wherein heat is generated within the cabinet. The apparatus comprises a heat exchanger having internal and external chambers surrounding heat pipe coils attached to the analyzer cabinet. The internal side chamber is in. communication with the cabinet via an inlet and an outlet; a continuously operating constant speed fan located in the inlet is provided for circulating air past the coils and through said cabinet. The external chamber is in communication with fresh outside ambient air and a variable speed fan circulates outside ambient air through the external chamber. A temperature sensor located in the cabinet produces signals corresponding to the temperature t at the senso~ocation. The variable speed fan is responsive to-.the signals produced,by the sensor.
The other. embodiment of this invention is an improved process for controlling the internal cabinet temperature of a near-infrared analyzer, and therefore, the-accuracy :_il., :,"',.a!'., i_ r-yi i !°1.'tu r.. ~ 2 ~WO 96105545 , 219 6 l 5 8 PCTIUS95108968 of the analyzer. This improvement comprises continuously measuring thetemperature of the critical optical components in the cabinet, and, in response, continuously circulating temperature-controlled air by these critical optical components to maintain the components at a relatively constant temperature. By use of this process, v the temperature of the temperature-sensitive critical optical components can be maintained to plus or minus O.I
degree C.
Brief Description of the Drawing The Figure is a schematic illustration of an analyzer and associated internal and external heat exchangers. -Detailed Description of the Preferred Embodiment Referring to the Figure analyzer, cabinet 10 contains critical optical systems 12, in addition to electrical -components (not shown). "Critical optical systems" or "critical optical components' are meant to include photodetectors, gratings, grating mounts, etc., which are temperature sensitive and are normally housed inside the analyzer cabinet in what is called an "optical bench."
Temperature sensor 14 is attached to the critical optical systems and outputs a temperature signal to temperature -controller 15. Also,-attached to analyzer cabinet 10 is a heat pipe heat exchanger 16, having an internal side 16a, an external side 16b, and heat pipe coils 18. The heat pipe coils extend from the internal side to the external aide so that heat may be transferred from the internal side to the external side. In addition, the internal side has an internal inlet 20 for removing air from the analyzer cabinet, and an internal outlet 22 for providing temperature-controlled air to the critical optical systems. A continuously operating internal fan 24 is mounted in the internal outlet 22 to provide movement of air through the internal side of the heat pipe heat exchanger. The external side 16b of the heat pipe heat exchanger has an external inlet 28 for providing fresh outside ambient air to the heat-pipe heat exchanger, and VI'O 96105545 _ 219 6 7 5 8 PC1YU595I08968 an external outlet 30 for removing this air from the external side_ A speed-controlled fan 32 is mounted in the external outlet 30 to provide movement of air through the external side of theheat pipe heat exchanger 16. The v speed controlled fan 32 is electrically connected to the S
temperature controller 15, and the speed of the fan increases or decreases based on the output signal from the , temperature sensor 14, thus providing more or less cooling to the heat pipe coils 18 in heat exchanger 16.
In one example of a preferred construction, a Noren Model CC600F heat pipe heat exchanger containing interior and exterior fans (supplied by Noren Products, Inc., Menlo Park, CA) was attached to the enclosure of a Guided Wave 300P Near-Infrared Analyzer- (supplied by UOP Guided Wave, I5 E1 Dorado Hills, CA). A Minco foil-type 100 ohm Resistance Temperature Detector, or RTD, was attached to critical optical components in the analyzer and inputted signals to a ECS Model 6415 PID temperature controller having a 10 amp control output. This output was in turn connected to the external fan of the heat pipe heat exchanger for;control of the external fan speed.
Thermal management-in instrument packaging has always been an impcrtant design consideration. Internal temperature control or near-infrared (NIR? analyzers is-essential for measurement precision. More particularly, NIR spectrophotometers- can be affected by temperature variations as little as 2.to 4degrees C, which cause shifting of optimal wavelengths, and the addition of error -in the measurement.
The typical process spectrophotometer is controlled within.a band cf temperature by utilization of an on-off type control strategy. In the "on" state, a condenser or .__. -other device is turned on to remove heat build-up from within the spectrophotometer enclosure as is described in U.S. Pater_t No. 4,328,676. The condenser or other device remains "on" until a low temperature limit is reached anal then the condenser is turned "off." The-temperature in -the spectrophotometer enclosure rises from the heat generated by the electronics and/or tile external environment until a second temperature limit is reached, which causes the condenser or other device to be turned -"on" again. This on/off temperature control approach commonly al7.ows the internal temperature to cycle 2-~ C
degrees..
SLT~!aZ'V of th Tnvon t i nn A preferred temperature control strategy was devised to remove heat from the analyzer and control the optical bench temperature continuously at aim. A temperature sensor is fastened to the optical bench in an analyzer to serve as a measurement input device for a control strategy which is truly aim-seeking.- The control strategy employs w heat pipe heat exchanger to remove heat from the F~Ai~~,7~~ ~H~Gi WO 96105545 , 219 6 7 5 8 PGTIUS95I08968 analyzer enclosure. A heat pipe utilizes a fluid (such as an alcohol) to remove heat by evaporation of the fluid at an internal air circulation heat exchanger and then recondensing the fluid at an external air circulation heat exchanger. Heat pipes are particularly useful in that internal cabinet air, not outside air, is circulated through the critical optical components, thereby , eliminating the need for additionalfiltering of the cooling air.
A PID temperature controller achieves the desired temperature setpoint by manipulation of heat exchanger fan speeds. The heat removal rate can be very precisely controlled..,T~ practice, both heat exchanger fans could be controlled._together; however, to,achieve optimal internal temperature uniformity, the internal heat exchanger fan-is maintained at full speed and just the external fan is controlled to adjust heat removal rate.
Optical-bench temperature control is maintained to plus or minus 0.1 degree C vs. a typical temperature control range of plus or minus 2 degrees C.
More particularly, the invention includes an apparatus and-a process for controlling the temperature of an analyzer cabinet wherein heat is generated within the cabinet. The apparatus comprises a heat exchanger having internal and external chambers surrounding heat pipe coils attached to the analyzer cabinet. The internal side chamber is in. communication with the cabinet via an inlet and an outlet; a continuously operating constant speed fan located in the inlet is provided for circulating air past the coils and through said cabinet. The external chamber is in communication with fresh outside ambient air and a variable speed fan circulates outside ambient air through the external chamber. A temperature sensor located in the cabinet produces signals corresponding to the temperature t at the senso~ocation. The variable speed fan is responsive to-.the signals produced,by the sensor.
The other. embodiment of this invention is an improved process for controlling the internal cabinet temperature of a near-infrared analyzer, and therefore, the-accuracy :_il., :,"',.a!'., i_ r-yi i !°1.'tu r.. ~ 2 ~WO 96105545 , 219 6 l 5 8 PCTIUS95108968 of the analyzer. This improvement comprises continuously measuring thetemperature of the critical optical components in the cabinet, and, in response, continuously circulating temperature-controlled air by these critical optical components to maintain the components at a relatively constant temperature. By use of this process, v the temperature of the temperature-sensitive critical optical components can be maintained to plus or minus O.I
degree C.
Brief Description of the Drawing The Figure is a schematic illustration of an analyzer and associated internal and external heat exchangers. -Detailed Description of the Preferred Embodiment Referring to the Figure analyzer, cabinet 10 contains critical optical systems 12, in addition to electrical -components (not shown). "Critical optical systems" or "critical optical components' are meant to include photodetectors, gratings, grating mounts, etc., which are temperature sensitive and are normally housed inside the analyzer cabinet in what is called an "optical bench."
Temperature sensor 14 is attached to the critical optical systems and outputs a temperature signal to temperature -controller 15. Also,-attached to analyzer cabinet 10 is a heat pipe heat exchanger 16, having an internal side 16a, an external side 16b, and heat pipe coils 18. The heat pipe coils extend from the internal side to the external aide so that heat may be transferred from the internal side to the external side. In addition, the internal side has an internal inlet 20 for removing air from the analyzer cabinet, and an internal outlet 22 for providing temperature-controlled air to the critical optical systems. A continuously operating internal fan 24 is mounted in the internal outlet 22 to provide movement of air through the internal side of the heat pipe heat exchanger. The external side 16b of the heat pipe heat exchanger has an external inlet 28 for providing fresh outside ambient air to the heat-pipe heat exchanger, and VI'O 96105545 _ 219 6 7 5 8 PC1YU595I08968 an external outlet 30 for removing this air from the external side_ A speed-controlled fan 32 is mounted in the external outlet 30 to provide movement of air through the external side of theheat pipe heat exchanger 16. The v speed controlled fan 32 is electrically connected to the S
temperature controller 15, and the speed of the fan increases or decreases based on the output signal from the , temperature sensor 14, thus providing more or less cooling to the heat pipe coils 18 in heat exchanger 16.
In one example of a preferred construction, a Noren Model CC600F heat pipe heat exchanger containing interior and exterior fans (supplied by Noren Products, Inc., Menlo Park, CA) was attached to the enclosure of a Guided Wave 300P Near-Infrared Analyzer- (supplied by UOP Guided Wave, I5 E1 Dorado Hills, CA). A Minco foil-type 100 ohm Resistance Temperature Detector, or RTD, was attached to critical optical components in the analyzer and inputted signals to a ECS Model 6415 PID temperature controller having a 10 amp control output. This output was in turn connected to the external fan of the heat pipe heat exchanger for;control of the external fan speed.
Claims (4)
1. An apparatus for continuously controlling to within plus or minus 0.1°C the temperature of an analyzer cabinet having critical optical components wherein heat is generated within said cabinet, said apparatus comprising: a heat exchanger having internal and external chambers surrounding heat pipe coils, said heat exchanger attached to said analyzer cabinet; said internal chamber being in communication with said cabinet by means of an inlet and an outlet; a continuously operating constant speed fan located in said inlet for circulating air past said coils and through said cabinet; said external chamber being in communication with fresh outside ambient air; and a variable speed fan circulating outside ambient air through said external chamber; a temperature sensor located in said cabinet on the critical optical components within said analyzer cabinet; said sensor producing signals corresponding to the temperature at the sensor location; and said variable speed fan being responsive to said signals,
2, The apparatus of claim 1, wherein the critical optical components are of the group consisting of a photodetector, a grating, and a grating mount.
3. In the process for controlling at an aim point within plus or minus 0.1°C the internal cabinet temperature of a near-infrared analyzer having critical optical components housed within a cabinet wherein a heat exchanger having internal and external chambers surrounding coils attached to the analyzer cabinet, the internal side of the chamber in communication with the cabinet via an inlet and outlet wherein a continuously operating constant speed fan circulates air past the coils and through the chamber and the external chamber communicates with fresh, outside ambient air via an inlet and outlet having a variable speed fan, the improvement comprising:
(a) continuously measuring the temperature of the critical optical components in cabinet by means of a temperature sensor fastened to the critical components;
and (b) continuously circulating temperature-controlled air by means of the constant speed fan past the critical optical components to maintain the components at a relatively constant temperature;
(c) controlling the speed of the variable speed fan from signals generated by the temperature sensor.
(a) continuously measuring the temperature of the critical optical components in cabinet by means of a temperature sensor fastened to the critical components;
and (b) continuously circulating temperature-controlled air by means of the constant speed fan past the critical optical components to maintain the components at a relatively constant temperature;
(c) controlling the speed of the variable speed fan from signals generated by the temperature sensor.
4. The process of claim 3, wherein the critical optical components are of the group consisting of a photodetector, a grating, and a grating mount.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/289,554 | 1994-08-12 | ||
| US08/289,554 US5523563A (en) | 1994-08-12 | 1994-08-12 | Apparatus for controlling the temperature of a near-infrared analyzer |
| PCT/US1995/008968 WO1996005545A1 (en) | 1994-08-12 | 1995-07-21 | Temperature control of near-infrared analyzer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2196758A1 CA2196758A1 (en) | 1996-02-22 |
| CA2196758C true CA2196758C (en) | 2006-02-28 |
Family
ID=36011113
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002196758A Expired - Fee Related CA2196758C (en) | 1994-08-12 | 1995-07-21 | Temperature control of near-infrared analyzer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2196758C (en) |
-
1995
- 1995-07-21 CA CA002196758A patent/CA2196758C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2196758A1 (en) | 1996-02-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |